Recently, because of potential risks involved with donated blood, methods for inactivating pathogenic agents that may be found in donor blood or blood components are being actively investigated. One of the most promising approaches is inactivating pathogenic agents by photochemical treatment. One of the main problems in most photochemical treatment methods is reducing the residual photosensitizer or its decomposed products in the treated blood to sufficiently low level so that the treated blood or blood product can be transfused to patients. Even though all donor blood is tested for possible contamination with known pathogens it is currently not possible to completely eliminate all contaminated blood from the donor blood pool.
This is caused by several circumstances. For instance, when a person is infected with viruses such as human immunodeficiency viruses (HIV) which causes AIDS, there is a period during which the anti-HIV antibody titer is too low for positive detection by current screening tests. Therefore, blood donated by an HIV infected person during this period may pass the antibody screening tests and could infect any recipients of the donated blood or blood products made therefrom. Also, there is always the possibility that the donated blood is contaminated by unknown or undetected pathogens. For these reasons currently there is an urgent need for methods to eliminate those undetected pathogens in the donated blood or blood components derived therefrom for human use.
Wiesehahn et al. (U.S. Pat. Nos. 4,727,027; 4,748,120; and 5,176,921) and Isaacs et al. (U.S. Pat. No. 5,139,940) described methods for deactivating pathogens in biological fluids by UVA irradiation in the presence of psoralen derivatives such as 8-methoxy psoralen(8-MOP), 4'hydroxymethyl-4,5',8-trimethylpsoralen (HMT), 4'-aminomethyl-4',5'8-trimethylpsoralen(AMT), or other psoralen derivatives. In this process only a small fraction of the total amount of psoralen compound added is consumed in inactivating those pathogens and the remainder of the added psoralen compound either remains in the treated blood as original psoralen compound or remains in the treated blood as psoralen decomposition products.
The amount of these residual compounds in the treated blood or blood component could be very substantial and when a patient is transfused with this treated blood or blood component the patient may be exposed to psoralens or psoralen degradation products. This exposure to psoralens or psoralen degradation products may in turn cause undesirable effects on the patient such as phototoxicity or other toxic effects associated with psoralen and their decomposition products. Therefore, it is highly desirable to remove the remaining psoralen derivatives or decomposed psoralen products from the treated blood or blood component before any human use.
Currently there are no methods published which have been shown to remove the psoralen compounds and their decomposition products from blood and blood products.